Selective photocatalytic oxidation of furfural to C4 compounds with metal-TS-1 zeolite

A series of metal-TS-1 zeolite catalysts were designed to selectively catalyze the photo oxidation of furfural to C4 carboxylic acid derivatives at ambient temperature and pressure. The photocatalytic preparation of malic acid from furfural was realized for the first time. The selective distribution of products could be controlled by adjusting the physical and chemical characteristics of the catalyst. Smaller pore size prevented the further conversion of maleic acid to malic acid; moderate acidity was beneficial for the preparation of malic acid; lower valence band was in favor of maleic acid production while higher valence band tended to form malic acid. The synergistic effect of pore structure, acidity and energy band structure of catalysts affected the product distribution. The yield of maleic acid reached as high as 40% over Fe-TS-1, meanwhile, the yield of malic acid reached as high as 63% over Ni-TS-1. The doping of metal was believed to be an effective procedure to adjust the structure and physicochemical properties of zeolite. Matel-TS-1 zeolite was also expected to be widely used in photocatalytic system to achieve more selective reactions.